Photosensitive element containing a photoreducible palladium compound and the use thereof in physical development

ABSTRACT

Light-sensitive palladium compounds are reduced on exposure to actinic light to nuclei which are catalytic centers for the deposition of metal from a physical developer. The palladium nuclei are catalysts for deposition of metal from stable physical developers, which developers do not respond to catalysts used in the physical development of silver latent images.

United States Patent Yudelson et a1. March 6, 1973 PHOTOSENSITIVEELEMENT [56] References Cited CONTAINING A PHOTOREDUCIBLE PALLADIUMCOMPOUND AND THE UNHED STATES PATENTS USE THEREOF IN PHYSICAL 2,267,95312/1941 Schumpelt ..96/88 X 3,011,920 12/1961 Shipley ..l17/213DEVELOPMENT 3,157,502 11/1964 Jonker et al .96/48 PD [75] Inventors:Joseph S. Yudelson, Rochester;

Henry J. Gysling, Bronx both of FOREIGN PATENTS OR APPLICATIONS 764,9595/1967 Italy ..96/48 [73] Assignee: Eastman Kodak Company,

Rochester NY Primary Exammer-J. Travis Brown Assistant Examiner-Won H.Louis, Jr. [22] Filed: July 13, 1967 Att0rneyWilliam H. J. Kline andJames R. Frederick [21] Appl. No.: 653,025 [57] ABSTRACT Light-sensitivepalladium compounds are reduced on [52] "96/48 96/48 96/48 exposure toactinic light to nuclei which are catalytic 96/88 117/34 centers for thedeposition of metal from a physical developer. The palladium nuclei arecatalysts for [51] Int. Cl ..G03c 5/24, G03c 1/00 deposition f meta] fStable physical developers, I which developers do not respond tocatalysts used in [58] Field of Search .....96/88, 48, 48 PD, 90; 117/34 the physical development of silver latent images.

10 Claims, No Drawings PHOTOSENSITIVE ELEMENT CONTAINING APHOTOREDUCIBLE PALLADIUM COMPOUND AND THE USE THEREOF IN PHYSICALDEVELOPMENT cerns the amplification of a latent image by the depositionof metal from a developer bath comprising a metal salt or complex and areducing agent. The bath is formulated so that it is stable underconditions of storage,

but in the presence of a catalyst, such as the latent image, itdecomposes and deposits reduced metal on catalytic sites. Once acatalytic site is enveloped with metal deposited from the bath it isessential that the reduced metal be autocatalytic, that is, it too mustcatalyze the decomposition of the bath.

Physical development involving silver compounds is well known. However,such processes have not had any substantial application due to the factthat silver physical developer solutions are extremely unstable. Thus,shortly after a physical developer bath is prepared by mixing silversalts and reducing agents, reduced silver begins to deposit rapidly, sothat in a few hours the bath is completely decomposed and is useless.This type of instability is inherent in silver physical developer bathsbecause of the autocatalytic properties of silver metal.

Physical developer baths which are stable under storage conditions canbe formulated from salts or complexes of some metals other than silver;however, these stable physical developer baths do not respond to thecatalysts which are commonly used in silver physical development, suchas colloidal silver, zinc sulfide, nickel sulfide, etc.

Therefore, it is an object of this invention to provide new and improvedphotographic elements and processes.

It is a further object of this invention to provide novel photographicprocesses wherein photographic images are developed with relativelystable physical developers.

It is a still further object of this invention to provide novelprocesses where the only steps necessary to produce stable photographicimages are exposure and physical development.

It is another object of this invention to provide novel elements whichcan be used in physical development processes.

The above and other objects of this invention will become apparent tothose skilled in the art from the further discussion of the inventionwhich follows.

In accordance with the present invention there is provided aphotographic element containing a lightsensitive palladium compoundwhich on exposure to actinic light forms catalytic centers or sites forthe deposition of metal from a physical developer. Catalytic centers orsites are formed by photoreduction of the palladium compound toelemental palladium, or to a compound which is readily reduced toelemental palladium. After exposure the element can be washed to removeunexposed palladium compound, or in some embodiments this washing is notrequired. The element is then contacted with a physical'developercomprising a heavy metal salt, a complexing agent for the metal salt anda reducing agent. In a preferred embodiment the palladium nuclei formedby exposure act as catalytic centers or sites for the deposition ofmetal from a bath of the physical developer. They constitute a-laten'timage which is formed by exposure and which is developed and givendensity by building up a deposit of metal thereon from the physicaldeveloper bath. In another embodiment the element is contacted with areceiving sheet containing the physical developer and the unexposedpalladium compound migrates to the receiving sheet where it is reducedand developed.

A wide variety of light-sensitive palladium compounds such as salts andcomplexes of palladium are useful in the elements of this invention.Light-sensitive palladium compounds which are useful in the practice ofthe present invention include those having the general formula:

- tPd(L).1.M. (n where L is a ligand such as a halogen ligand such asbromine, chlorine, or iodine, a carboxylic acid ligand such as amalonate group, anoxalate group, etc., and aromatic ligand such asphenol, styrene, naphthol, etc., a nitrogen ligand such as ammonia, anamine such as methyl amine, ethyl amine, benzyl amine, propane diamine,tetraethylene pentamine, aminoethanol, methylaminoethanol,am'inonaphthol, bipyridine, phenanthroline, ethylenediamirietetraaceticacid, etc., a nitrile such as nitrilotriethanol, benzonitrile, etc., animine such as iminodiethanol, an oxime such as salicylaldoxime or anazide such as benzhydrazide, a phosphorous ligand such astriarylphosphine, trialkylphosphine, etc., an arsenic ligand such astriarylarsine, trialkylarsine, etc., an antimony ligand such astriarylantimony, trialkylantimony, etc., and the like; M is an ion suchas a hydrogen ion, an inorganic acid ion such as a chloride ion, abromide ion, an iodide ion, a sulfate ion, a nitrate ion, a phosphateion, etc., an organic acid ion such as an acetate ion, an acrylate ion,an ion, a malonate ion, etc., a metal ion such as a sodium ion, apotassium ion, a calcium ion, a strontium ion, an aluminum ion, etc., anonium ion such as those'containing nitrogen, phosphorus or sulfur like aquaternary ammonium ion, a quaternary phos'phonium'ion, a tertiarysulfonium ion, etc., and the like, or M can be a [Pd(L group; x is aninteger from 0 through 4; y is an integer from 1 through 4; z is aninteger from 0 through 2, and x and z are not 0 at the same time.

Light-sensitive compounds of Formula (I) which are useful in the presentinvention include: palladium diammine dichloride, palladium styrenedichloride, palladium di(tributylphosphine) dichloride, palladiumdi(benzonitrile) dichloride, palladium di(triphenylphosphine)dichloride, palladium di(triphenylarsine) dichloride, palladiumdi(triphenylantimony) dichloride, palladium di(l-naphthol) dichloride,palladium di(2-naphthol) dichloride, palladium di(S- amino-l-naphthol)dichloride, palladium di(benzylamine') dichloride, palladiumo-phenylenediamine dichloride, palladium l,l0-phenanthroline dichloride,palladium 2,2-bipyridine dichloride, palladium di(benzyhydrazide)dichloride, palladium salicylaldoxime dichloride, palladiumdi-(N-phenyl-Z- naphthylamine) dichloride, and potassium palladouschloride.

tetrammine di(tetraphenylboride), palladium ethylenediamine dichloride,palladium di(l,3- propanediamine) dichloride, palladiumtetra(methylamine) dichloride, palladium triethylenetetraminedichloride, palladium tetra- (tetraethylenepentamine) dichloride,palladium tetra(Z-diethylaminoethanol) dichloride, palladiumtetra(2-aminoethanol) dichloride, palladium tetra(2 methylaminoethanol)dichloride, palladium tetra(nitrilotriethanol) dichloride, palladiumtetra(2,2'-iminodiethanol) dichloride, palladiumtetra(triphenylphosphine) dichloride, palladium tetrammine dichloride,palladium tetrammine dibromide, palladium dia'mmine oxalate, palladiumtriphenylarsine oxalate, palladium di(triphenylantimony) oxalate,palladium 2,2'-bipyridine oxalate, palladium 1,10- phenanthrolineoxalate, palladium oxalate, potassium palladium oxalate, potassiumpalladium malonate, palladium tetrammine palladium dioxalate andpalladium tetrammine palladium tetrachloride.

Light-sensitive palladium compounds useful in the practice of thepresent invention can be prepared by techniques known to those skilledin the art. Preparation of some of the palladium compounds useful in thepresent invention are shown in Examples 1, 3 and 6. Preparative methodsfor other palladium'compounds can be found in such works as Encyclopediaof Chemical Reactions, C.A. Jacobson; Reinhold Publishing Corp. N.Y.;Vol. 'V, i953, pp. 301-321; and Tretise on Inorganic and TheoreticalChemistry, G.W. Mellor; Longmans Green & Co., N.Y., Vol. XV, 1936, pp.654-685.

The physical developer which is used to produce a visible image cancomprise an aqueous bath in which is dissolved a salt of a heavy metal,a complexing agent for the metal ion', and reducing agent. The physicaldeveloper bath is chosen so that deposition of the heavy metal from thebath is catalyzed by palladium nuclei produced on exposure. The heavymetal deposited from the bath must itself be autocatalytic; that is, itmust act as a catalyst for further deposition of metal from thedeveloper. This is necessary in order that deposition and developmentwill continue after palladium nuclei are enveloped with heavy metal.With respect to the Periodic Table, suitable heavy metals can beselected from Group VIII metals such as nickel, cobalt, iron, palladiumand platinum, Group VIB metals such as chromium and Group IB metals suchas copper, silver and gold. Almost any heavy metal salt which is asource of the desired heavy metal ions can be employed. Suitable heavymetal salts useful in the invention include heavy metal halides such ascobaltous bromide, cobaltous chloride, cobaltous iodide, ferrousbromide, ferrous chloride, chromium bromide, chromiurn chloride,chromium iodide, copper chloride, silver bromide, silver chloride,silver iodide, gold chloride, palladium chloride and platinum chloride,heavy metal sulfates such as nickel sulfate, ferrous sulfate, cobaltoussulfate, chromium sulfate, copper sulfate, palladium sulfate andplatinum sulfate, heavy metal nitrates such as nickel nitrate, ferrousnitrate, cobaltous nitrate, chromium nitrate and copper nitrate, andheavy metal salts of organic acids such as ferrous acetate, cobaltousacetate, chromium acetate and copper formate. Baths can be formulatedbased on a single heavy metal or based on mixtures of heavy metals. Whenmore than one heavy metal is employed in the bath, the image which isdeposited will generally be an alloy of the two metals. Physicaldevelopers based on noble metals such as silver, gold and platinum arerelatively unstable and cannot be stored for long periods of time.However, such physical developers are operative in the processes of thisinvention and can be employed if the developer bath is prepared shortlybefore use.

The complexing agent employed in the physical developer bath should tieup the metal ions so that they show a lessened tendency to be reducedspontaneously. However, the complexing agent should not bind the metalions so tightly that they will be unable to be reduced. and deposited onthe latent image sites in the presence of the catalyst. Suitablecomplexing agents include ammonium salts such as ammonium chloride,organic acids such as aspartic acid, malic acid, citric acid, glycolicacid, salts of organic acids such as sodium citrate, potassium citrate,sodium glycolate, potassium glycolate, sodium succinate, potassiumsuccinate, potassium sodium tartrate, etc. A single complexing agent canbe used or a combination of more than one complexing agent can beincorporated in the physical developer bath. 7

The reducing agent can be any compound which provides a ready source ofelectrons for the reduction of the metal ions and which does nototherwise interfer with development. A general criteria for a reducingagent useful in the physical developers of the present invention is thatthe potential of the chemical couple of the reducing agent, written asfollows:

Reducing agent: Products electrons must be more positive than that forthe metal or metals which are to be deposited from the bath. Forexample, the potential for the nickel couple:

NiF-"Ni* 2 electrons is +0.27? volts for acidic solutions. It isnecessary for the reducing agent to possess a potential that is greater,i.e., more positive, than +0.277 volts in order that it be capable ofreducing nickel ions in the bath. Suitable reducing agents includehypophosphites such as sodium hypophosphite, manganous hypophosphite,potassium hypophosphite, etc., hydrosulfites such as sodiumhydrosulfite, potassium hydrosultite, calcium hydrosulfite, etc.,borohydrides such as sodium borohydride, potassium borohydride, etc.,hydrazines, and the like.

There can be added to the physical developer bath a variety of othermaterials such as buffering agents, acid or base to adjust the pH,preservatives, etc. in accordance with usual practices.

The proportions in which the various components of the physicaldeveloper are present in the bath can vary over a wide range. Suitableconcentrations of metal salt in the developer bath are in the range offrom about 0.01 to about 0.5 moles of metal salt per liter of bath. Theupper limit of concentration is controlled by the solubility of theparticular metal salt employed. Preferably, the bath is between about0.05 molar and 0.25 molar with respect to metal salt. The relativeproportions of metal salt and complexing agent are dependent upon theparticular metal salt or salts and the particular complexing agent oragents which are employed. As a general rule sufficient complexing agentshould be incorporated to bind the metal ions and lessen the tendency ofthe metal ions to be reduced prior to use of the developer. Dependingupon the particular metal salt and complexing agent employed, the amountof complexing agent present can vary from about 4 mole to about moles ofcomplexing agent per mole of metal salt present. The reducing agent canbe present in amounts of from about 0.1 moles to about 5 moles ofreducing agent per mole of metal salt present.

In preparing photosensitive elements utilizing the palladium compoundsof this invention, the palladium compound can be imbibed in or coated ona support, or it can be incorporated in a self-supporting binder.

When the palladium compound is imbibed in a support, an aqueous solutionof the compound is prepared and a porous support is'immersed in thesolution. After drying a photosensitiveelement is obtained.

Suitable porous supports include paper, coated paper, porcelain,polymeric films, such as are described hereinafter, on which is coatedsuch porous materials as gelatin, olefinic polymers such as polyvinylalcohols, polyvinyl phthalates, etc., carboxyl containing polymers suchas carboxymethyl cellulose, cellulose ether phthalates, cellulose ethersuccinates, cellulose ether maleates, copolymers of alkyl acrylates withacrylic acid, etc., and the like.

The amount of palladium compound that is taken up in the supportgenerally varies from about 2 to about 25 mg. of palladium/ft. Theamount which is absorbed by a polymer coating on film base is dependenton the nature and coverage of the polymer, the degree to which it hasbeen crosslinked, the temperature of the imbibing bath, and the pH ofthe bath. Coverages as low as 2 mg. of palladium/ft are adequate whenusing development conditions described herein. The photographic speedwill increase with increasing concentration of the light-sensitivepalladium compound. The preferred coverage is generally in the range ofl0 to 25 mg. of palladium/ft.

When the palladium compound is coated on a support, it is generallycoated with a hydrophilic binder. A solution or dispersion of thepalladium compound and binder is formulated, and after thorough mixingit is coated on the support by any well-known coating process such ashopper coating, doctor-blade coating, dip coating, swirl coating, spraycoating, etc.

Suitable binders in which the palladium compounds of the presentinvention can be incorporated include gelatin such as bone gelatin,pigskin gelatin, etc.; olefinic polymers such as polyvinyl alcohol,polyvinyl phthalates, etc., carboxyl containing polymers such ascarboxymethyl cellulose, cellulose ether phthalates,

cellulose ether succinates, cellulose ether maleates,

copolymers of alkyl acrylates with acrylic acid, etc.,

and the like. Non-hydrophilic polymers such as ethyl cellulose can beused in procedures which do not involve imbibition and where the coatingcomposition is a stable dispersion which gives a porous coating upondrying. Such a coating is described in Example 8.

The palladium compound-binder composition can be coated from aqueoussolution, or it can be coated from an organic solvent. In someinstances, where an organic solvent is employed, the palladiumcompound-binder composition will form a water-in-oil type dispersionwith the organic solvent. Suitable solvents include water immissiblehydrocarbon solvents such as benzene, toluene, etc.; halogenatedhydrocarbons such as methylene chloride, ethylene chloride, carbontetrachloride, etc.; and the like. Mixtures of such solvents can beemployed advantageously in the practice of this invention.

In preparing the coating compositions utilizing the palladium compoundsdisclosed herein useful elements are obtained where palladium is presentin an amount equal to at least about 0.5 weight percent of the coatingcomposition. The upper limit in the amount of palladium present can bevaried widely. When a binder is employed, palladium is normally presentin an amount from about 0.5 weight percent of the coating composition toabout 20 weight percent of the coating composition. A preferred weightrange for palladium in the coating composition is from about 1 weightpercent to about 10 weight percent.

Coating thicknesses of the palladium compound binder compositions on asupport can vary widely. Normally, a wet coating thickness in the rangeof about 0.001 inch to about 0.01 inch is useful in the practice of theinvention. A preferred range of coating thickness is from about 0.002inch to about 0.007 inch before drying, although such thicknesses canvary depending upon the particular application contemplatedfor'theelement.

Suitable supports for coating the palladium compound-binder compositionsof the present invention include paper, polyethylene-coated paper,glassine, vegetable parchment, polymeric films such as polystyrene film,cellulose nitrate film, cellulose acetate film, celluloseacetate-butyrate film, cellulose acetate-propionate film,polyethylene-terephthalate film, polyethylene-sebacate film,polyethylene-adipate film, etc., and the like. In some embodiments ofthis in? vention, a separate support need not be utilized, the binderacting as the support material.

Elements prepared according to the present invention can be exposed bytechniques well known to those skilled in the art of photography. Sincethe compounds of this invention exhibit their greatest sensitivity inthe blue and near ultraviolet regions, light sources rich in suchradiation are preferably employed. Exposure to actinic light causes thereduction of the palladium compound to nuclei of elemental palladiumwhich act as catalytic centers or sites for the deposition of metal fromthe physical developer. Depending upon the light source and theparticular palladium compounds, exposure times of from several secondsto several minutes give satisfactory latent images.

. Development of exposed elements can be efl'ected by contacting theelement with a physical developer bath, for example by immersion, for aperiod of time sufficient to produce an image of the desired density.The time required to deposit a satisfactory heavy metal image from thephysical developer bath on the element can vary from 1 second to severalhours depending upon the composition of the particular bath beingemployed, the density of heavy metal image desired, and the temperatureof the bath. Satisfactory images can be produced from baths at roomtemperature (20 C.) or at elevated temperatures. Bath temperature offrom 20 C. to 100 C. are preferred.

Development can also be effected using a diffusion transfer process. Insuch a process the photosensitive element is exposedin the usual mannerand is then contacted with a receiving sheet into which has been imbibedone of the physical developer solutions described above. When theelement and the receiving sheet are in contact, heat is applied topromote diffusion of unexposed palladium compound from the, element tothe receiving sheet. Contact temperatures of from 45 C. to 100 C. aresuitable. In the unexposed areas of the element the palladium compoundmigrates from the element to the receiving sheet where it is reducedandcatalyzes the reduction of heavy metal salt in the sheet to form apositive image on thereceiving sheet. In the exposed areas the palladiumcompound does not migrate as rapidly because of the smaller differentialin concentration of palladium compound between the ex posed areas of theelement and the receiving sheet which results from the formation ,ofpalladium nuclei on exposure and the reduction of palladium compound inthe vicinity of these nuclei. Thus, the difference in concentration ofthe palladiumcompound in exposed and unexposed areas of the elementpermits the transfer of sufficient palladium compound to the receivingsheet from unexposed areas of the' element before a significant amountof palladium compound has been transferred from exposed areas of theelement. Although the image formed on the receiving sheet can be used assuch, in some instances it is preferred that the image be darkenedfurther by immersing the receiving sheet in one of the physicaldeveloper baths described herein.

The physical developer solutions which are imbibed into the receivingsheet differ somewhat from the physical developer baths used forimmersion development in that they contain a greater proportion of heavymetal salt and reducing agent and a lesser proportion of complexingagent. The additional reducing agent is required to effect reduction ofthe unexposed palladium compound. The ratio of reducing agent to metalsalt can be thesame as described above, although ratios of from about 1to' about 5 moles of reducing agent per mole of metal salt arepreferred. The ratio of complexing agent to metal salt is lower than therange indicated above. Ratios of 'complexing agent to heavy metal saltof from about 0.5 moles to about 2.0-moles of complexing agent per moleof heavy metal salt are preferred. As in the case of the baths discussedabove, these ratios will vary depending upon the particular metal saltand complexing agent employed.

The photosensitive compositions and elements of thisinvention find usein a wide variety of applications Elements containing the photosensitivepalladiumcompounds of this invention can be exposed to actinic radiationthrough a subject to be copied such as a trans parency, and can then bedeveloped with an appropriate physical developer bath. In this mannerthe processes and elements of this invention can be used to producepositive'or negative copies from originals and continuous tone and linenegatives for a variety of use for which systems based on silver areemployed. Properties of certain of the heavy metal images can beutilized for specialized applications. For example, ink receptive metalscan be used to produce lithographic printing masters, electricalconducting metals can be used to prepare printed circuits, and magneticmetals can be used to prepare magnetic images or records.

The ink receptive properties of the heavy metal deposited from thephysical developer bath can be employed advantageously to makelithographic plates. Elements used to prepare such lithographic platesand masters require that the support and binder used be hydrophilic.Thus, after exposure and development, the heavy metal image areas willreadily receive ink while in background areas, where heavy metal has notbeen deposited, ink will be repelled by the hydrophilic support orbinder. These elements should be developed for a period of timesufficient to deposit from the developer bathenough heavy metal to maskthe hydrophilic properties of the substrate in image areas. While thedensity of heavy metal required will vary depending upon the particularsubstrate and heavy metal employed, and the conditions under which ithas been deposited, a heavy metal image density of about 1 gram/squarefoot or greater is generally sufficientto mask the hydrophilicproperties of the substrate.

The electrical conductive properties of images of such heavy metals ascopper, iron, nickel, etc., can be employed to produce printed circuitsusing the elements and process of this invention. For such applications,the supports and binders used should be non-conductive.

The invention is further illustrated by'the' following examples whichinclude preferred embodiments thereof.

EXAMPLE 1 Four grams of potassium chloride were dissolved in 150 ml ofwater and 2.5 gm. of palladium chloride (PdCl were added to thissolution, The mixture was stirreduntil all of the palladium chloride wasdissolved. The solution was evaporated on a steam bath to a volume of 50ml. and cooled in an ice bath. The resulting crystals were washed twicewith cold water, then washed with ethanol and then ether. They weredried at room temperature. The yield of potassium palladous chloride(K,PdCl,) was approximately percent based on the palladium chloride. Astrip of water-leaf paper-stock was impregnated with a dilutelone-halfpercent) solution of potassium palladous chloride. After drying, theimpregnated strip was exposedto a 350 watt mercury are at a distance ofl4-inches for one minute. The stripwas then washed for several minutesin running water to remove unexposed palladium compound. It was thenimmersed in the following cobalttype physical developer at C.

Cobaltous chloride caci sino 1.5 g.

Aspartic acid HOCOCHNH,CH,COOH 20.0 g. Sodium hypophosphite NaH,PO,'H,O7.5 g. Water to make 1 liter After a one-minute immersion, the exposedareas of the strip had a density of 0.8 and the unexposed areas remainedessentially unchanged.

EXAMPLE 2 EXAMPLE 3 Palladium tetrammine chloride (Pd(NH Cl was preparedby dissolving palladous chloride in concentrated ammonium hydroxide,then lowering the pH of the solution to 6.0 with hydrochloric acid. Apaper strip was impregnated with a dilute solution (0.5 percent) of thiscomplex and dried. After drying, the strip was exposed as described inExample 1. The strip was developed by immersion for two seconds in thefollowing nickel-type physical developer at 90 C.

Nickel chloride NiCl,-6H,O 30 Sodium hypophosphite NaH,PO,-H,O l g.=Ammonium chloride 50 g.

Water was added to make one liter of solution and the pH was adjusted to9.0 with ammonium hydroxide. The exposed areas of the strip developed toa density of 1.5 whereas the unexposed area remained unchanged.

EXAMPLE 4 A paper strip was impregnated with palladium tetramminechloride as in Example 3 and dried. The strip was exposed with a mercuryare as described in Example 1, and was developed by immersion for fiveseconds in the following iron-type physical developer at 75 C.

Ferrous sulfate FeSO.-7H,O 30 g. Rochelle salt (KNa Tartrate) 50 g.Sodium hypophosphite NaHJ'Oyl-LO 10 g.

Water was added to make one liter of solution and the pH was adjusted to9.1 with concentrated ammonium hydroxide. The exposed areas of the stripdeveloped to a density of 0.5 whereas the unexposed area remainedessentially unchanged.

EXAMPLE 5 A paper strip was impregnated with potassium palladouschloride as in Example 1 and dried. The strip was exposed to a mercuryarc as described in Example 1. The exposed strip was then washed forseveral minutes in running water to remove unreacted palladium compound.It was then developed by immersion in the following chromium-typephysical developer for seconds at 99 C.

Chromium acetate CrAc, 30 g. Sodium acetate NaAc-3H,O 20 g. Sodiumglycolate 40 g.

Sodium citrate 'S-Vz H,O

40 g. Sodium hypophosphite -H,O

EXAMPLE 6 Potassium palladium oxalate (K,Pd0x was prepared as follows.Two grams of potassium palladous chloride were dissolved in 20 ml. ofwater. Another solution was prepared consisting of 10 grams of potassiumoxalate (K Ox-H O) in 40 ml. of water. The two solutions were mixedtogether and stirred for 10 minutes at room temperature. The precipitatewhich formed was filtered and washed with ethanol until thefiltrate wasfree of chloride ion. It was then washed briefly with ethyl ether anddried at room temperature. The yield of potassium palladium oxalate wasapproximately 60 percent based on potassium palladous chloride. Twopaper strips were impregnated with a dilute solution (0.5 percent)ofqthis complex and dried. One of the strips was then exposed behind anegative to a 350 watt mercury arc at l4-inches distance forone, minute.The second strip was exposed through a line copy negative to a 250 wattphoto-flood lamp (GE No. 2) at l 2-inches distance for one minute. Bothsamples were developed by immersion for five minutes in the followingnickel-type physical developer at 60 C.

Nickel sulfate NiSOflil-LO 23.7 g. I Sodium hypophosphite NaH,PO,-H,023.9 g. Malic acid (DL) HOCOCHOHCI-LCOOH 48.2 g. Sodium succinate(CH,COO),Na,6H,O 16.2 g.

Water wasadded to make one liter of solution. The pH of the solution was6.0. The exposed areas of both strips showed densities above 1.0. Theunexposed areas had densities less then 0.01.

EXAMPLE 7 The following solution was prepared; Poly(vinyl alcohol) (soldas 71-30" by E.l. DuPont De Nemours & Co.), 5 percent aqueous solution10 g. Palladium tetrammine chloride (0.5 percent solution) 10 ml. Boricacid (1 percent solution) 1 ml. The above solution was coated on apoly(vinyl alcohol) subbed polyester film base using an 0.005 inchcoating knife. After drying it was exposed behind a negative to a 350watt mercury are at a distance of 14 inches for one minute. It wasdeveloped by immersion for 15 seconds in the cobalt-type physicaldeveloping bath described in Example 1. The exposed area of the filmstrip had a density of over 1.0 whereas the unexposed area remainedtransparent.

EXAMPLE 8 Ten ml. of the coating solution described in Example 7 wasdispersed in 20 ml. of a 3.5 percent solution of ethyl cellulose (soldas T-lO, by the Hercules Chemical Co.) in toluene by means of a blender.A stable water-in-oil dispersion was obtained. A coating of thedispersion was made on paper using a 0.005 inch knife and dried. Thecoated element thus obtained was exposed and developed as in Example 7.The exposed area of the strip had a density exceeding 1.0 whereas theunexposed area had a density of less than 0.01

EXAMPLE 9 A strip of poly(ethylene terephthalate) support coated withgelatin at a coverage of 350 mg. of gelatin/ft was immersed into a 0.5percent solution of potassium palladium oxalate (K PdOx whose pH hadbeen lowered to 2.0 by the addition of p-toluenesulfonic acid. Afterminutes immersion, the film was wiped, dried, and exposed for 30 secondsthrough a line copy negative to an exposure unit drawing 1000 wattsdistributed among a small fan and 28 tungsten bulbs. The bulbs are 2-%inches from the negative during exposure. The film was then developedfor 3 seconds in the nickel-type physical developer of Example 3. Theareas of film which had been exposed to light developed to a densitygieater than 2, whereas the unexposed areas of the film remained clear,thus resulting in a good quality positive copy of the original negative.A sample of the film which had been imbibed with a potassium palladiumoxalate solution whose pH had not been lowered required a 2-% minuteexposure in order to obtain a good image using the same developmentprocedure.

EXAMPLE 10 A strip of paper was immersed into a 0.5 percent solution ofpotassium palladium oxalate whose pH had been lowered to 2.8 by theaddition of oxalic acid. After 10 minutes immersion, the paper was driedand exposed for 7 seconds through a line copy negativeto the exposureunit described in Example 9. It was then developed for 3 seconds in thenickel physical developer of Example 3. A good quality positive printwas obtained. A sample of the film which had been imbibed with apotassium palladium oxalate solution whose pH had not been lowered fromits original value (5.8) required an exposure of- 30 seconds in order toobtain a good'image using the development conditions describedabove.

EXAMPLE 11 A paper strip was impregnated with palladium tetramminechloride and dried. it was'exposed as described in Example 7 anddeveloped for 1 minute at 25 C. in a physical developer containingcopper ions and a reducing agent (sold as Enplate CU-400" by Enthone,Inc.) The exposed areas of the strip had a dark image whereas theunexposed areas had a very faint image.

EXAMPLE l2 with the following physical developer to form a 6 processingweb and receiver.

Nickel chloride 0.6 molar Malic acid 0.6 molar Sodium hypophosphite 0.6molar Water to make I liter Concentrated ammonium hydroxide added toraise the pH to 7.0

The web was placed against the exposed film, and

EXAMPLE 13 A subbed polyethylene-coated paper support on which is coateda heavy layer of a titanium dioxidegelatin mixture was soaked in a 0.5percent potassium palladium oxalate (K,Pd0x,) solution at pH 2.8. Thesheet was exposed through a negative line image by means of a bank ofeight 8-wa tt black-light tubes (GE F8T5-BL) for 30 seconds at adistance of 2 inches. It was then developed for approximately 2 minutesin the nickel physicaldeveloper solution of Example 3 at C. A heavymetallic nickel image appeared on the sheet in the exposed areas,whereas the unexposed areas remained free of metal. The developed sheetwas put on an offset printing press, wet with fountain solution (adilute acid) and then inked with an oil-based ink. The plate took up inkin the nickel image'ar eas and the background remained ink free. Severalimpressions were made using this printing master. The adhesion of themetal image to the support was excellent.

EXAMPLE 14 A sheet of baryta coated paper was soaked in a 0.5 percentsolution of potassium palladium oxalate adjusted to pH 2.8. The treatedsheet was exposed through a negative line image as .in Example 13. Itwas then developed for approximatelyZ-hbu'rs in the nickel physicaldeveloper of Example 6 at room temperature. A heavy metallic nickelimage appeared on the sheet in the exposed areas whereas the unexposedareas remained free of metal. The developed sheet was soaked in waterand inked with lithographers" ink. The sheet was then pressed against asheet of bond paper and gave an excellent ink transfer. The sheet was.reinked and the procedure carried out for several impressions. There wasno change in the wettability characteristics of the master with extendeduse.

EXAMPLE 1s A sheet of polyethylene-coated paper on which had been coateda mixture of titanium dioxide and polyvinyl alcohol was soaked in a 0.5percent solution of potassium palladium oxalate adjusted to pH 2.8. Thesheet was exposed through a negative line image by means of a bank ofeight 8-watt black-light tubes for 30 seconds at a distance of 2 inches.It was then developed for approximately 1 minute in a copper physicaldeveloper solution at room temperature. The physical developerwasprepared by mixing five parts of the following solution with one partof a 37 percent formal- 5 dehyde solution.

35 gm. gm.

Triethanolamine (HOC,H );N l3 gm.

Disodium ethylene diaminetet'raacetic acid 6.5 gm. g Sodium hydroxide 50gm. Sodium carbonate l7 gm. Water to make 1 liter The developed sheetshowed an excellent copper image in the exposed areas. It was put on anoffset printing press, wet with fountain solution, and inked with anoilbased ink. The plate showed good inking differentiation and severalprints were made with this printing master? EXAMPLE 16 A sheet of lightweight water-leaf paper was impregnated with a 0.5 percent solution ofpalladium tetrammine chloride and dried. It was then exposed to a 350watt mercury arc at a distance of 14 inches for one minute behind anegative which contained a line pattern. The exposed sheet was thenimmersed for five seconds at 90 C. in the following nickel type physicaldeveloper:

Nickel chloride (NiCl,'6H,O) 30 gms. Sodium hypophosphite (NaH,PO,-H,O)gms. Ammonium chloride (NH Cl) 50 gms.

Water was added to make one liter and the solution was adjusted to pH 9with ammonium hydroxide. An excellent image appeared which showed aresistance of 50 ohms/square.

EXAMPLE 17 An absorbent porcelain plate (Streak Plate" sold by the WillCorporation) was dipped briefly in a 0.5 percent solution of potassiumpalladium oxalate and dried. lt was-exposed as in Example 16 behind anegative which contained a line pattern. The plate was then immersed forthree minutes at 95 C. in the following nickel physical developer:

Nickel chloride (NiCl,-6H,O) 30 gms. Sodium hypophosphite (NaH,PO,-H,O)10 gms. Sodium citrate (Na,C.H,O,'5 /&H,O) 100 gms. Ammonium chloride(NPLCI) 50 gms.

Water was added to make one liter of solution and it was adjusted to pH9 with ammonium hydroxide. An excellent image was formed which showed aresistance of 40 ohms/square.

EXAMPLE 18 A sheet of poly(ethylene terephthalate) film base coated withgelatin at a coverage of 350 mg. of

as described above and as defined in the following claims.

We claim:

1. A photosensitive element comprising a support and a light-sensitivecompound which on exposure to actinic light forms catalytic centers forthe deposition of metal from a physical developer, said compound havingthe formula [Pd(L),],, Mz, wherein L is a ligand, selected from thegroup consisting of halogen ligands, carboxylic acid ligands, aromaticligands, nitrogen ligands, phosphorous ligands, arsenic ligands, andantimony ligands; M is selected from the group consisting of ionsselected from the group consisting of hydrogen ions, inorganic acidions, organic acid ions, metal ions selected from the group consistingof sodium ions, potassium ions, calcium ions, strontium ions, andaluminum ions, and onium ions, and [Pd(L) groups; x is an integer from 0throughz4; y is an integer from 1 through 4; ,z is an integer from 0through 2;

and x and z are not 0 at the same time. 2. A photosensitive element asdefined in claim 1, wherein at least a part of the support is porous andthe light-sensitive palladium compound is imbibed therein.

3. A photosensitive element as defined inclaim- 1, wherein thelight-sensitive palladium compound is coated on the support in ahydrophilic binder.

4. A photosensitive element as defined in claim 1, wherein thelight-sensitive palladium compound is selected from the group consistingof potassium palladium oxalate, palladium oxalate, palladium tetramminechloride, palladium tetrammine bromide, and potassium palladouschloride.

5. A photosensitive element comprising a support and a light-sensitivecomposition comprising potassium palladium oxalate;

6. A method of producing photographic images comprising the steps of l.imagewise exposing to actinic light a photosensitive element comprisinga support and a light-sensitive palladium compound, wherein thelight-sensitive palladium compound has the formula [Pd(L),],, Mz,wherein L is a ligand, selected from the group consisting of halogenligands, carboxylic acid ligands, aromatic ligands, nitrogen ligands,phosphorous ligands, arsenic ligands, and antimony ligands;

M is selected from the group consisting of ions selected from the groupconsisting of hydrogen ions, inorganic acid ions, organic acid ions,metal ions selected from the group consisting of sodium ions, potassiumions, calcium ions, strontium ions, and aluminum ions, and [Pd(L),groups; x is an integer from 0 through 4; y is an integer from 1 through4;

z is an integer from 0 through 2; and x and z are not 0 at the sametime, and 2. developing the latent image thus formed with a physicaldeveloper comprising a reducible heavy metal salt selected from thegroup consisting of nicket salts; cobalt salts, iron salts, chromiumsalts, copper salts, and mixtures thereof, a complexing agent for heavymetal ions from saidsalt and a reducing agent for heavy metal ions fromsaid salt. 7. A method of producing photographic-images as defined inclaim 6, further comprising the stepof washing the element betweenexposure and development to remove unexposed palladium compound.

1. imagewise exposing to actinic light a photosensitive elementcomprising a support and a light-sensitive palladium compound, whereinthe light-sensitive palladium compound has the formula (Pd(L)x)y Mz,wherein L is a ligand, selected from the group consisting of halogenligands, carboxylic acid ligands, aromatic ligands, nitrogen ligands,phosphorous ligands, arsenic ligands, and antimony ligands; M isselected from the group consisting of ions selected from the groupconsisting of hydrogen ions, inorganic acid ions, organic acid ions,metal ions selected from the group consisting of sodium ions, potassiumions, calcium ions, strontium ions, and aluminum ions, and (Pd(L)x)groups; x is an integer from 0 through 4; y is an integer from 1 through4; z is an integer from 0 through 2; and x and z are not 0 at the sametime, and
 1. A photosensitive element comprising a support and alight-sensitive compound which on exposure to actinic light formscatalytic centers for the deposition of metal from a physical developer,said compound having the formula (Pd(L)x)y Mz, wherein L is a ligand,selected from the group consisting of halogen ligands, carboxylic acidligands, aromatic ligands, nitrogen ligands, phosphorous ligands,arsenic ligands, and antimony ligands; M is selected from the groupconsisting of ions selected from the group consisting of hydrogen ions,inorganic acid ions, organic acid ions, metal ions selected from thegroup consisting of sodium ions, potassium ions, calcium ions, strontiumions, and aluminum ions, and onium ions, and (Pd(L)x) groups; x is aninteger from 0 through 4; y is an integer from 1 through 4; z is aninteger from 0 through 2; and x and z are not 0 at the same time.
 2. Aphotosensitive element as defined in claim 1, wherein at least a part ofthe support is porous and the light-sensitive palladium compound isimbibed therein.
 2. developing the latent image thus formed with aphysical developer comprising a reducible heavy metal salt selected fromthe group consisting of nicket salts, cobalt salts, iron salts, chromiumsalts, copper salts, and mixtures thereof, a complexing agent for heavymetal ions from said salt and a reducing agent for heavy metaL ions fromsaid salt.
 3. A photosensitive element as defined in claim 1, whereinthe light-sensitive palladium compound is coated on the support in ahydrophilic binder.
 4. A photosensitive element as defined in claim 1,wherein the light-sensitive palladium compound is selected from thegroup consisting of potassium palladium oxalate, palladium oxalate,palladium tetrammine chloride, palladium tetrammine bromide, andpotassium palladous chloride.
 5. A photosensitive element comprising asupport and a light-sensitive composition comprising potassium palladiumoxalate.
 6. A method of producing photographic images comprising thesteps of
 7. A method of producing photographic images as defined inclaim 6, further comprising the step of washing the element betweenexposure and development to remove unexposed palladium compound.
 8. Amethod of producing photographic images as defined in claim 6, whereindevelopment is accomplished by immersing the exposed element in a bathof the physical developer.
 9. A method of producing photographic imagesas defined in claim 6, wherein development is accomplished by contactingthe exposed element with a receiving sheet containing the physicaldeveloper and heating the element to cause migration of unexposedlight-sensitive palladium compound from the element to the receivingsheet, where it is reduced and developed.